Definitely "Godzilla vs. Biollante" (1989). In the 80s they came out with a new Godzilla film yearly, timed to coincide with the start of school winter vacation (12/26-1/5 roughly). I took DS every year. We saw Mothra, King Ghidorah, etc and so of course we headed off to see this one too. Dark screen, scary suspenseful music (think the first Batman movie) . The camera slowly pans up from water level up, up, up, this twisted trunk of vines until it reaches the head of the beast(musical crescendo), a red rose!
This year's monster was an overgrown red rose bush with a bad temper.....I was instantly gone....I had to duck into my winter coat, I was laughing so hard. DS didn't see the hilarity. We didn't buy the monster that year, to add to the collection (still have the Mothra grub and moth, and a huge King Ghodorah
Edited to correct an omitted word.